A prior art push-button switch is shown in FIG. 1. A contact section 102 is coupled in back of a push button operation section 101, wherein this contact section 102 is provided with terminal metal fixtures 103, 103 electrically connected to a fixed contact and a movable contact, and washer-attached terminal screws 104, 104 as mated therewith.
Also, a prior known transformer-attached indicator lamp is shown in FIGS. 2 and 3. A transformer section 122 is coupled in back of an indicator section 121, and a terminal section 123 is coupled in further back of it. As shown in FIG. 3, terminal fixtures 124, 125 electrically connected to the primary winding of a transformer are provided at the right and left sides of a substantially square back surface and symmetrical with respect to the center point, wherein terminal screws 126, 127 are disposed at diagonally opposing corners for being mated with threaded holes of the terminal fixtures 124, 125. These terminal screws 126, 127 are provided to be rotatable relative to square washers 128, 129 but not detachable therefrom, and also arranged so that the terminal fixture portions opposing such washers 128, 129 are exposed from a terminal section housing.
In these prior art devices, where the terminal screw 104 of the contact section 102 or the terminal screws 126, 127 of terminal section 123 are connected with ring-like contact-bonding terminal-attached lead wires by way of example, it is required that the terminal screw 104 or screws 126, 127 be completely unlocked for release and then mated again. This would result in an increase in wiring process step number while simultaneously raising a risk of occurrence of electrical shorting of circuitry at drop-out portions due to missing of terminal screws and/or dropping down thereof, which disadvantageously serves to further increase difficulty in screwing the washer-attached terminal screws into corresponding terminal fixtures when sufficient spaces are not present near or around them.
Seeing the prior art technology as to terminal base plates for mere connection between lead wires by extending the technical field, Japanese Patent Publication No. 4-11988 or Japanese Utility Model Registration Publication No. 3-7031 discloses therein a terminal base having terminal fixture with a vertical piece integrally provided therewith and a coil spring (recovery spring) as disposed between the distal end of such vertical piece and a housing.
When the automatic recovery structure of such terminal bases is adapted for use with terminal devices as employed in control elements such as push button switches and the like, positioning of the coil spring at the lower part of the vertical piece requires use of certain space corresponding to the length of coil spring compressed, which results in an increase in height of the contact section--in other words, the terminal section increases its depth dimension. This disadvantageously serves to much reduce the product value of control elements which have received strong demands for miniaturization. In addition, each coil spring must be laterally inserted during fabrication while forcing it to be compressed thus increasing complexity of assembly works, which in turn renders difficult automation of assembly.
The above Japanese Utility Model Publication No. 3-7031 also discloses therein another terminal base structure which includes a compression coil spring as provided on the front side (terminal screw side) of a terminal fixture, and an insertion section for support of the center portion of such coil spring, which section is arranged to penetrate through the terminal fixture from the front to the back side thereof thereby supporting an associated terminal screw.
However, the automatic recovery structure of this terminal base is faced with problems which follow: Where this device is adapted for use in controller elements, resultant structure is increased in total depth dimension due to the fact that the insertion section projects toward the back side of the terminal fixture when a terminal screw is locked; furthermore, a connection lead wire or contact-bonding terminal can be accidentally clipped between adjacent twisted wires of the coil spring due to exposure of the coil spring on the surface of such terminal fixture.
A further terminal base is disclosed in Published Unexamined Japanese Utility Model Registration Application No. 2-27666, which base is structured as shown in FIG. 4, wherein a washer guide section 112 is provided by bending downwardly a lower vertical elongate piece formed at one side of a washer supporting at its neck section a terminal screw 110 and is arranged to penetrate a terminal fixture 111 from its upper to lower side. The the coil section of a torsion coil spring (recovery spring) 114 is attached for support of spring 114 to each shaft 113 formed beneath the terminal fixture with its one free edge being engaged with the lower end of washer guide section 112.
The prior art suffers from a problem in that when the automatic recovery structure is adapted for use in terminal devices as employed in controller elements such as push button switches and the like, assembly works are difficult rendering automation likewise difficult due to the necessity of attaching the coil section of each torsion coil spring 114 to its associated shaft 113 and then engaging it with the lower end of the washer guide section 112 while pushing the torsion coil spring 114 for resilient displacement. Another problem is that the resulting depth size is enlarged since the torsion coil spring 114 is disposed beneath the terminal screw 110 and located on an extension line from the axis direction of terminal screw 110.
In the recent years a finger protect structure is increasing in importance more and more for use in control elements or control equipment. This refers to a specific structure for protection by use of dielectric materials to suppress an accidental finger touch in view of the fact that if electrically conductive then current-carrying portions such as head sections of terminal screws are exposed raising a risk of occurrence of electrical shocks.
One prior art approach to such finger protect structure is shown in FIG. 5 by way of example, wherein a detachable finger protect cover 106 is attached onto a contact section main body 105 so as to cover terminal screws 104. Another approach is depicted in FIG. 6, wherein finger protect pieces 108, 108 are rigidly attached by adhesive so as to cover the head sections of terminal screws 104, 104 of a contact section main body 107. Unfortunately, any one of these approaches suffers from an increase in parts number as a whole; especially, the former approach of employing the finger protect cover 106 is associated with a problem in that the finger protect cover 106 can drop down and that attachment thereof might be forgotten after once taken out.
Accordingly, an object of the present invention is to provide a terminal device capable of avoiding the foregoing problems encountered with the prior art, more particularly a terminal device capable of easily attaining automatization based on the fact that while it has an automatic recovery structure for eliminating drop-down of washer-attached terminal screws while forcing them--when unlocked--to be automatically spaced apart from terminal fixtures, the device does not increase in depth size as a whole, and yet capable of being assembled merely by putting into a specified space without having to apply in advance pressure to a recovery spring during assembly.